Lesvos is not a main tourist destination; therefore there are relative few direct charter flights from EU countries. You can of course always come via Athens or Thessalonica. Aegean/Olympic as members of Star Alliance can be combined with companies like British Airways or Lufthansa and your baggage is checked through to Mytilini (MJT), your final destination.
You can of course use low-cost companies like EasyJet and Ryanair. In this case you often fly with handbag only and then you can also use smaller Greek companies like Astra or Skyexpress for your Mytilini flight.
If you wish to check flight possibilities on-line we suggest Skyscanner.
Below we give you an idea how the situation was with direct flights from Europe in 2019. Obviously, it is impossible to preview flights in 2021...